1. Field of the Invention
The present invention relates to a rubber dam which traverses a spillway of a dam (movable) or a river, and dams up water and to a method of application thereof.
2. Description of the Related Art
As shown in FIG. 8, an arch rubber dam 30 as a dam which dams up the running of a river and adjusts the amount of running water has been put to practical use.
This arch rubber dam 30 is applied in the following manner. A rubber sheet 32 is doubled up and overlapped so as to form a bag shape. The bag-shaped rubber sheet 32 is placed on an overflow dam 14 which is built on a river bed. A seam portion 32A of the bag-shaped rubber sheet 32 is fixed to the summit portion of the overflow dam 14 by bolts 20 so that the rubber sheet 32 is formed in an arch shape.
When the rubber sheet 32 is curved in an arch shape, due to the difference of curvature, the rubber sheet 32 is strained in the longitudinal direction at the fixed side thereof (at the upstream side). Accordingly, when the rubber sheet 32 is collapsed, a force by which the rubber sheet 32 is contracted toward the upstream side acts upon the rubber sheet 32, and as shown in FIG. 9, the rubber sheet 32 bulges in portions at the downstream side. In this way, if the rubber sheet 32 bulges, when the rubber sheet 32 is collapsed, it may be hit by drift wood or the like, and abrasions or damage may be caused.
When two end portions of the rubber sheet 32 are fixed to side surfaces of fixed dams in this manner, since the rubber sheet 32 bulges along the slope surface of the overflow dam 14, applicability is inferior.